Maximizing the reliability of the data in disk drives is a key objective of disk drive designers. Unfortunately, that objective often conflicts with the similarly important need for performance. That is, by increasing the reliability performance measures, such as the data transfer rate, could suffer. For example, when data is written to the disk drive, the success of the write operation, i.e., whether the media accepted the data is unknown. One sure way to guarantee the success of a write operation is by re-reading the recorded data after each write operation. However, a technique that requires all data written to be read as well would severely degrade the performance of the drive. On the other hand, such verification would ensure high reliability of the data.
As explained above, these conflicting demands are particularly relevant during write operations. By contrast, if an error occurs during a read operation, the offending section of data can be re-read. However, errors occurring during write operations are more likely to result in permanent data loss.
Write errors are often transient. That is, if the error was detected and the write re-attempted the write would be successful. For example, write errors caused by dust particles might be corrected if re-attempted. Such contaminants could temporarily displace the recording mechanism, which results in an error during the write operation. Significantly, these transient write errors are particularly prevalent in removable media disk drives. Applicants have recognized that during the use of such removable media drives, the media is repeatedly removed and reinserted, increasing the likelihood of contaminants entering the cartridge.
Thus, there is a need for a method to detect transient write errors and to ensure a more reliable write operation while minimizing any performance penalty.